Considering the fact that the 942 board accomodates the expanded memory bus and uses an 8-layer PCB, it doesn't carry a huge premium over the R200 boards it succeeds due to the level of integration in the R300 ASIC (although I guess if some sources have to step up to 10 layers to maintain SSTL_2 integrity it will be more costly). Of course, the ASIC itself is costly.
The RV250 is a masterpiece of economical design; the 964 boards cost 25% less to manufacture than nVidia's equivalent and the ASIC is obviously cheap to produce. Understandably, the margins are going to be great. Even 958, with its BGA-packaged RAM, should be much cheaper than any R200 board ever was to manufacture. The DCs are cheap too; just 4-layer PCBs that actually cost less than the Ripper 2 chips themselves.
MuFu.